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Common Technical Issues : CBR900RR Fireblade (93-95)

These bikes have what is called a "permanent magnet system" for charging the battery, consisting of a 3-phase stator, a permanent magnet flywheel or rotor, and a separate regulator/rectifier.

The 3-phase stator has three output wire leads which feed into the regulator/rectifier unit. This unit rectifies the AC coming from the stator into DC power and regulates it to around 14.5Vdc. The output wire leads from the regulator/rectifier connect to the battery through a main fuse.

These permanent magnet systems have proven to be very reliable overall, which is why they have been used on almost all motorcycles for the past 40 years.

MOST COMMON FAILURES:

1) The stator can quit producing power usually due to the insulation failing. This is commonly caused by age or overheating.

2) The regulator/rectifier can have one or more rectifier diodes fail, which causes the output to drop to zero, or it can have the regulation circuit fail which causes the output voltage to be unregulated and liable to climb past 16Vdc.

And to help with testing a rectifier bridge in the regulator/rectifier we have created a special Diode Testing Guide.

As always: ensure you have good connections everywhere. Simply disconnecting every connector on the bike one by one, spraying with contact cleaner, and reconnecting goes a long way towards reliability.

When replacing stators: ensure you seat the stator completely in the case without pinching any wire leads. Check to make sure the screws that bolt the stator down are tight, and ALWAYS use thread locking compound such as Locktite to prevent the screws from working themselves loose. Also replace the alternator cover gasket and use some liquid gasket on the rubber grommet to ensure 100% sealing.

Most importantly: Solid and clean electrical connections are the key to a reliable system. We cannot stress this enough!

Contact ElectroSport if you cannot find the problem. We will be happy to assist you in diagnosing your charging system.